New drugs, old problems: immune checkpoint inhibitors and cancer-associated thrombosis

A frequent side effect of cancer treatment is venous thromboembolism (VTE), which is made more likely by systemic anticancer medication. Immune checkpoint inhibitors (ICIs) have emerged as a paradigm-shifting treatment for many cancers. Early trials investigating the efficacy of ICIs did not identify thrombosis as a significant adverse event of concern. An initial meta-analysis reported a 1.1% [95% confidence interval (CI) 0.5-2.1] risk of arterial thromboembolism (ATE) and a 2.7% (95% CI 1.8-4.0) rate of vein thrombosis. ICIs have, however, been linked to ATE and VTE in an increasing number of post-marketing investigations. The reported incidence rates of cumulative VTE range from 5-8% at 6 months to 10-12% at 12 months, while the rates of ATE vary from 1-2% at 6 months to 17 months. Furthermore, a number of studies show a correlation between reduced survival and ICI-related thromboembolism. In order to provide a compiled and thorough narrative on the mechanisms, incidence, risk factors, and survival related to ICI-associated VTE and ATE, this narrative review summarizes the literature.